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BIG PHYSICS, BIG QUESTIONS –

Cold War waste fouls the Clyde

By Rob Edwards

TOXIC waste thrown overboard by the US Navy has transformed Holy Loch on the Clyde estuary into one of the dirtiest stretches of coastal water in the world, according to reports commissioned by Britain’s Ministry of Defence. But MoD plans to clean up the Scottish loch, which was a US nuclear submarine base until five years ago, could make the problem even worse by threatening human health, says one of Britain’s leading marine scientists.

Two reports presented to the MoD last month by the Edinburgh-based consultancy firm Environmental Resources Management (ERM) reveal that concentrations of heavy metals, PCBs and other toxic chemicals in the loch are far higher than in other estuaries in Britain, and frequently in breach of safety limits. New Scientist obtained copies of the reports, marked “confidential” and “restricted”, from an unofficial source after both the MoD and ERM failed to provide them, although the MoD insists that the reports are not secret.

Holy Loch was used to refit US nuclear-powered submarines between 1961 and 1992. Home to up to 10 submarines carrying Poseidon nuclear missiles, a floating dry dock and a depot ship, it was the focus of frequent antinuclear protests over the years. Now its biggest problem is the 130 000 cubic metres of dangerous debris that the US Navy left behind.

Almost a quarter of the floor of the loch, which is 4 kilometres long and a kilometre wide, is covered with rubbish. There are several piles of debris up to six metres high around the sites in the middle of the loch where the dry dock and depot ship were moored. An MoD underwater video survey last year identified scores of different items, including a huge boiler, girders, ladders, air ducts, oil drums, washing machines and nine shipwrecks.

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Sampling carried out in December by ERM found maximum levels of nickel, chromium, zinc and copper in sediment over three times as high as in other British estuaries. One sample of sediment contained 228 milligrams per kilogram of the carcinogens known as polycyclic aromatic hydrocarbons. This is nearly six times the limit considered safe in the Netherlands, which is one of the few countries to have worked out marine standards for these pollutants.

Concentrations of the gender-bending chemical phthalate, which mimics the hormone oestrogen, reached 245 micrograms per litre of water-49 times the Dutch safety limit for groundwater. Water sampling also suggested concentrations of mercury, tin and copper in excess of European environmental quality standards. ERM did not look for radioactivity, but points out that an earlier survey of sediment by the MoD detected low levels of cobalt-60 and manganese-54 from submarine reactors.

The ERM reports disclose another MoD survey of Holy Loch in 1995, which found up to 864 micrograms of PCBs per kilogram of sediment. Graham Shimmield, director of the government-funded Dunstaffnage Marine Laboratory near Oban in Scotland, says this is the highest level he has heard of anywhere in the world.

Shimmield also argues that ERM’s sampling technique could have underestimated the scale of the pollution in the loch. The top 10 centimetres of sediment may be the worst contaminated, he says, but ERM samples came from deeper below the surface.

ERM concludes that if the debris is lifted carefully from the bottom of the loch “significant impacts on the environment are not expected”. This autumn the MoD, backed by the Scottish Environment Protection Agency and the local Argyll and Bute Council, plans to start clearing the loch of ferrous waste using a crane and a large electromagnet. Under a NATO agreement, the British government is responsible for decontaminating military bases in the UK abandoned by allied forces.

But Shimmield fears that disturbing the contaminated sediment might cause toxic chemicals to dissolve and be consumed by fish. Holy Loch is a celebrated source of Scottish sea trout and is fished for salmon. He points out that fine grains of contaminated silt could also be washed ashore and come into contact with people. It is also possible that the debris conceals nasty surprises such as containers of the highly toxic antifouling agent tributyltin.

Because Shimmield expressed his concerns to a local councillor, he was summoned to a private meeting with scientists from ERM and the MoD earlier this week. Although the MoD claims Shimmield was reassured by “some aspects” of the cleanup plans, he remains sceptical. “I still have concerns that the level of contamination in Holy Loch, if disturbed, could prove to be an environmental hazard,” he says. “The cleanup could cause more problems than it solves.”